The road finisher known from EP 0 484 236 A includes spraying facilities which are lateral bars distributed over the longitudinal extension of the road finisher. The spraying facilities are also offset laterally to the longitudinal axis of the road finisher, in order to e.g. produce three strip-shaped sprayed lanes which result behind the road finisher in a laterally continuous carpet. A first spraying bar is arranged in front of the undercarriage and sprays the planum between the travelling lanes of the undercarriage. Secondary spraying facilities are arranged behind the undercarriage in the rear section of the road paver in order to spray the travelling lanes. Third spraying facilities are arranged at the outer sides of the travelling lanes, in particular, in longitudinal direction between the front side and rear side spraying facilities in order to spray regions within the total working width outside of the undercarriage. The sprayed carpet is combined like a mosaic of single rectangular or parallelogram shaped sprayed fields, since the spraying facilities are moved in reciprocating fashion and since the spraying nozzles are deactivated when reversing the direction of movement. As the spraying system is constructed such that all spraying facilities are activated at the same time when starting a spraying process and are deactivated at the same time when a spraying process is terminated, a sprayed carpet results from the offset between the spraying facilities in travelling direction and lateral to the travelling direction, which sprayed carpet has front and rear boundaries which do not extend lineally and laterally to the travelling direction but define a profile with steps. However, as the front boundary and the rear boundary of the laid down cover layer extend lineally and straight laterally to the travelling direction of the road finisher, and since it has to be assured that the sprayed carpet extends over the entire working width to the front boundary and the rear boundary of the laid down cover layer, sections of the profiles having steps will remain without being covered by the laid down cover layer, due to the respective stepped profile of the front and rear boundaries of the sprayed carpet. This not only means a waste of bonding agent, but also an unnecessary pre-impregnation of the planum. For a new working start and when connecting a newly laid down cover layer to an earlier laid down cover layer, again a bonding agent has to be applied excessively with a stepped profile because the cover layer which has to be laid down, of course, needs fresh bonding agent over the working width in order to achieve a homogonous bonding effect. This multiplies the waste of the bonding agent. In order to overcome this drawback in practice the respective stepped profile is completed manually by using spraying splash lances. The use of splash lances, however, in most cases results in locally excessively sprayed down bonding agent, which then rather will act as a separation layer for the laid down cover layer (bonding faults) than a bonding layer. Furthermore, the use of the splash lances means undesirable environmental contamination by bitumen stench and spraying fog.
The road finisher known from DE 41 01 417 A carries a selectively removable spraying system comprising spraying bars at low positions behind the undercarriage which spraying bars not only spray the basic width of the paving screed but also comprise extension beams which can be moved sidewardly outwardly or can be pivoted outwardly. Mounting and manipulation of the extension beams are necessary for spraying the outside regions of the working width may easily lead to problems. Furthermore, mounting the spraying facilities in this area of the road finisher between the rear end of the road finisher and the lateral distribution device in front of the paving screed cause complicated space problems.
In the spraying road finisher known from DE 93 17 124 U different spraying facilities are mounted such that they are offset to each other in longitudinal direction and lateral direction of the road finisher. Secondary aggregates like pumps and filters common to all spraying facilities are mounted in a free space of the chassis. As soon as the secondary aggregates are switched on all spraying facilities are supplied at the same time with the bonding agent, and all spraying facilities start spraying processes at the same time. Due to the offset between the spraying facilities and the simultaneous activation or deactivation a stepped profile is produced at the front and rear boundaries of the sprayed carpet. This stepped profile does not fit to the linear an straight lateral front and rear boundaries of the laid down cover layer.
A distributing apparatus for bituminous material according to U.S. Pat. No. 2,372,065 A has a main bar extending laterally to the travelling direction. The main bar contains several spraying nozzles. At both ends of the main bar additional beams having nozzles are linked in pivotable fashion in order to vary the spraying width by a pivoting motion of the beams. Only when the beams are fully pivoted outwardly, a straight front boundary of the sprayed carpet can be achieved which extends laterally to the travelling direction. Whenever the working width is smaller than the full maximum working width the front boundary or the rear boundary of the sprayed carpet cannot be straight, lineal and lateral to the travelling direction. All nozzles are simultaneously supplied with bituminous material via a common valve assembly and a common pump activated or deactivated for a spraying process.